High performance forged aluminum connecting rod and method of making the same

ABSTRACT

An improved high performance aluminum connecting rod and a method of manufacturing such a connecting rod which is capable of carrying particularly high compressive loads with a substantially reduced deformation resulting from such high compressive loads in high performance engines. The connecting rod is made of an extruded bar stock forging made of an aluminum alloy material which is forged and machined to make the connecting rod. The connecting rod has a substantially increased compressive yield strength as well as a substantially increased tensile yield strength. This increase in the compressive yield strength of the connecting rod effectively prevents bending of the connecting rod beam, elongation of the wrist pin bore, and a marked deterioration in the roundness of the bearing housing bore.

RELATED APPLICATION

This application is a division of our U.S. patent application Ser. No.09/192,247, filed Nov. 16, 1998, now U.S. Pat. No. 6,134,779 issued onOct. 24, 2000 entitled Improved High Performance Forged AluminumConnecting Rod and Method of Making The Same.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to the field of manufacturingforged aluminum connecting rods, and more particularly to an improvedhigh performance aluminum connecting rod and a method for manufacturingsuch a connecting rod which is capable of carrying particularly highcompressive loads with a substantially reduced deformation resultingfrom such high compressive loads, the improved high performance aluminumconnecting rod of the present invention finding particular applicationin the field of high performance racing engines.

Internal combustion engines used in automobiles typically have pistonswhich reciprocate in cylinders contained in an engine block, with thepistons driving connecting rods which in turn drive a singlegeometrically complex crankshaft, causing it to rotate within the engineblock. The pistons are cylindrical and are hollowed out at the endfacing the crankshaft. Wrist pins extending diametrically through thepistons near the open end thereof are used to connect each piston to oneend of a connecting rod which has a cylindrical wrist pin bore locatedtherein, which end is referred to as the pin end of the connecting rod.

The other end of each connecting rod is connected to the crankshaft at aparticular cylindrical bearing location on the crankshaft. This end ofthe connecting rod, which is referred to as the crank end, also has acylindrical bearing housing bore located therein. Typically, an annularbearing is located between the bearing housing bore at the crank end ofthe connecting rod and the cylindrical bearing location on thecrankshaft.

The crank end of the connecting rod is split into two segments, with thesplit being defined by a plane which lies at an angle to thelongitudinal axis of the connecting rod (the axis extending between thepin end and the crank end of the connecting rod), which plane dividesthe bearing housing bore at the crank end of the connecting rod in half.The end of the main segment of the connecting rod (the segment whichincludes the pin end) which is opposite the pin end is referred to asthe fork of the connecting rod, since it includes half of the bearinghousing bore at the crank end of the connecting rod.

The smaller segment of the connecting rod is referred to as the cap orthe bearing cap, and it includes the other half of the bearing housingbore at the crank end of the connecting rod. The cap typically isretained in position on the fork by two bolts located on opposite sidesof the cap and fork. The bolts extend into holes located in the, cap,and are screwed into threaded apertures located in the fork.

As is generally well known in the art, the development of thereciprocating internal combustion engine has resulted in ever-smallerengines which are capable of generating an ever-increasing amount ofhorsepower, at ever-higher RPM's. It will be appreciated by thoseskilled in the art that with the increasing power has come increasedstresses which are placed on the various parts of the engine, includingincreased stresses placed on the connecting rods and bearings. Theseadvancements in engine technology have resulted in a demand forconnecting rods which are both lighter and stronger than previousgenerations of connecting rods.

Nowhere is this demand for improved connecting rod strength andlightness more important than in the field of auto racing, includinggas, alcohol, and nitro engines which are used in drag racing. Theseengines are subjected to incredible loads, and this is particularly truewith respect to the ultra high combustion pressure loads that theconnecting rods are subjected to. The loads are compressive in nature,and whenever the yield strength of the connecting rods is exceeded, theywill be damaged or destroyed. Typical damage which can result from thesestresses includes bending of the connecting rod beam (the portion of theconnecting rod extending between the pin end and the fork), elongationof the wrist pin bore, and deformation of the bearing housing bore,particularly in the cap of the connecting rod.

The materials which are used to make high performance connecting rodsare almost exclusively high tech aluminum alloys, which possess bothrelatively light weight and the requisite high degree of materialstrength. Aluminum alloys have been used for high performance enginessuch as those used in drag racing for thirty years, with the first alloybeing used being 2014-T6 aluminum alloy, which has a compressive yieldstrength of 58 ksi. More recently, 7075-T6 aluminum alloy has been used,which has a substantially higher compressive yield strength of 72 ksi.Neither of these alloys currently possesses sufficient compressive yieldstrength to withstand the compression loads of current drag racingengine technology.

In addition, the manufacture of high performance aluminum connectingrods from aluminum material must be of a nature which enhances, and inno way reduces, the material strength characteristics of the aluminummaterial. To understand this, it is necessary to briefly describe themanufacture of connecting rods. There are three primary methods ofmanufacturing connecting rods: casting, powder metal manufacturingrolled plate stock, and foregoing. Each of these methods will be brieflydescribed below.

Casting involves heating the metal alloy which will be used until it ismolten, and pouring the molten metal alloy into “sprews” which areconnected to “runners” which channel the molten metal alloy into amultiple cavity mold. The molten metal alloy fills the mold, and ventsthrough “risers.” After cooling, the metal casting is separated from themold, the sprews, runners, and risers are removed, and the casting ismachined.

Casting is a relatively low-cost manufacturing process, and results in aproduct with tight dimensional tolerances. Unfortunately, casting hasseveral disadvantages, including relatively low strengthcharacteristics, an absence of grain flow strength, and possibleporosity of the cast article.

These negative characteristics make casting an unacceptablemanufacturing process for high performance aluminum connecting rods.

Powder metal manufacturing involves placing a mixture of metal powderinto a preformed die, and then compressing the powder in the die with acompacting press to mechanically bond the metal powder into a preform.The preform is then sintered to chemically bond the powder in thepreform, and the preform is then heated and forged in a press. Theresulting article is then machined to finish it.

Powder metal manufacturing results in high tolerances and uniformmaterial composition of the finished article. Unfortunately, powdermetal manufacturing is a relatively high cost operation, has a lack ofgrain flow strength, and results in a product which has relatively lowtensile strength and impact strength. These negative characteristicsmake powder metal manufacturing an unacceptable manufacturing processfor high performance aluminum connecting rods.

The rolled plate stock approach includes machining to form a billetconnecting rod. However, the rod has relatively low strength and nograin flow strength.

Forging involves heating a piece of bar stock or rod stock (referred toas a forge slug) to a forging temperature, placing the heated forge sluginto a two piece forging die defining a cavity within, and forging theforge slug using a forging press or forging hammers with multipleimpacts. Excess material results in flashing extending between the twodies. This flashing is removed by placing the forging into a trim die,which is placed in a punch press to trim the flashing from the forgedarticle. The part is then machined to finished dimensions.

Forging can be somewhat labor intensive due to the amount of machiningwhich is necessary to produce the finished article, but it produces aproduct which has strength characteristics which are superior to thoseproduced by casting rolled plate stock or powder metal manufacturing.This results from the fact that the natural grain of rolled metal stockis maintained in the finished product. The natural grain extends alongthe full length of the forged rod, from one end where it is expanded.The natural grain is not truncated, as is the case with a billet. Assuch, it will be apparent to those skilled in the art that forging isthe preferred method of manufacture for high performance aluminumconnecting rods.

It is accordingly the primary objective of the present invention that itprovide an improved high performance aluminum connecting rod made of animproved material capable of withstanding the high compressive loads ofcurrent drag racing technology. The material used by the improved highperformance aluminum connecting rod of the present invention must havelightweight construction which is comparable to presently known highperformance aluminum materials such as 7075-T6, while possessingsubstantially enhanced compression yield strength characteristics ascompared to such presently known materials. In addition, this improvedmaterial must retain or enhance all of the other favorable materialcharacteristics of such presently known materials.

The improved high performance aluminum connecting rod of the presentinvention must be susceptible of manufacture by conventional forgingtechniques, with the forged part being readily machinable to therequired finished dimensions. It is also necessary that the highperformance characteristics of the aluminum material used to make theimproved high performance aluminum connecting rod of the presentinvention not be adversely affected in the forging or machiningoperations. Most importantly, it is an objective of the improved highperformance aluminum connecting rod of the present invention that ithave sufficiently improved compression yield strength so as to hold bothits dimensional length and the dimensional roundness of the wrist pinbore and the bearing housing bore.

The improved high performance aluminum connecting rod of the presentinvention must be of a construction which is both durable and longlasting, and it must remain within dimensional specifications throughoutan extended operating lifetime. In order to enhance the market appeal ofthe present invention, it should also be of relatively inexpensiveconstruction to thereby afford it the broadest possible market. Finally,it is also an objective that all of the aforesaid advantages andobjectives of the improved high performance aluminum connecting rod ofthe present invention be achieved without incurring any substantialrelative disadvantage.

SUMMARY OF THE INVENTION

The disadvantages and limitations of the background art discussed aboveare overcome by the improved high performance aluminum connecting rod ofthe present invention. With this invention, an improved high performancealuminum alloy is used as the material used to fabricate the improvedhigh performance aluminum connecting rod of the present invention. Thismaterial, which is a variant of the aluminum alloy taught in U.S. Pat.No. 5,221,377, to Hunt, Jr., et al., assigned of record to the AluminumCompany of America (Alcoa), has an improved combination of strength,density, and toughness, with a yield strength which is substantiallyhigher than aluminum alloys such as 7075-T6 which have previously beenused for connecting rods. U.S. Pat. No. 5,221,377 is hereby incorporatedherein by reference.

This improved high performance aluminum alloy is obtained in extrudedbar stock which is suitable for forging, either as rectangular bar stockor as round bar stock. The improved high performance aluminum alloy barstock is of a suitable size and is cut to an appropriate length. Thesegment of high performance aluminum alloy bar stock is heated to atemperature which was determined after extensive testing. The heatedsegment of high performance aluminum alloy bar stock is then forged in ablocker die to rough out the shape of a connecting rod. The rough partis forged in a finisher die, and is then cooled.

The flashing resulting from the foregoing process is cleaned off of theforged part in a trim die. The forged part is then heat treated andetched, as is conventional in the art, after which it is penetrantinspected and ultrasonically tested. The forged part is then ballburnished, completing the first portion of the manufacturing process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the improved high performance aluminumconnecting rod of the present invention will be described in detail, butfirst the high performance aluminum alloy from which it is manufacturedwill be described in detail. As mentioned above, this high performancealuminum alloy is a variant of the aluminum alloy taught in Alcoa's U.S.Pat. No. 5,221,377, which has previously been incorporated herein byreference. Prior to the development leading up to the improved highperformance aluminum connecting rod of the present invention, thisaluminum alloy has not been known to be suitable for the fabrication ofconnecting rods.

The preferred high performance aluminum alloy used to make the improvedhigh performance aluminum connecting rod of the present invention is analloy available from Aluminum Company of America “Alcoa” as 7055-T77511,also referred to as HP007. This aluminum alloy has been available fromAlcoa for some time, but never made into extruded bar stock for forging.By working with Alcoa, the inventors of the invention described hereinobtained 7055-T77511 aluminum alloy from Aluminum Company of America“Alcoa” in extruded bar stock suitable for forging. The 7055-T77511aluminum alloy used to fabricate the improved high performance aluminumconnecting rod of the present invention is formulated (by weight) asfollows: drilled into the fork of the connecting rod. The holes in thefork of the connecting rod are threaded.

The cap is assembled onto the fork of the connecting rod usinglubricated rod bolts, which are torqued to the proper degree. Bearingtangs and an oil-retaining aperture for a bearing retaining pin are alsomachined into the bearing housing bore, and an oil passage is machinedinto the wrist pin bore. The bearing housing bore is then rough bored,finish bored, and honed to the proper size. On the pin end of theconnecting rod, the wrist pin bore is bored and honed to the propersize.

The improved high performance aluminum connecting rod of the presentinvention has been found to possess a number of significant advantagesover previously-known connecting rods, with absolutely no attendantdisadvantages. The improved high performance aluminum connecting rod ofthe present invention has a substantially increased compressive yieldstrength as well as a substantially increased compressive yield strengthas well as a substantially increased tensile yield strength. Undertesting in drag racing engines generating in excess of 6,000 horsepower,the improved high performance aluminum connecting rod of the presentinvention has been found to have a compressive yield strength of 25percent greater than 7075-T6.

The increase in the compressive yield strength of the improved highperformance aluminum connecting rod of the present invention effectivelyprevents bending of the connecting rod beam, elongation of the wristpine bore, and a marked deterioration in the roundness of the bearinghousing bore. As compared to a conventional high performance aluminumconnecting rod made of 7075-T6, which typically experiences acompression of 0.004 to 0.005 inch after one run at full load, theimproved high performance aluminum connecting rod of the presentinvention remains within 0.001 inch of its original dimension after onerun at full load.

The wrist pin bore of the improved high performance aluminum connectingrod of the present invention remains within 0.0003 to 0.0005 inch of itsoriginal dimension after one run at full load, as compared to the wristpin bore of a conventional high performance aluminum connecting rod,which loses roundness of 0.002 to 0.003 inch after one run at full load.Finally, the bearing housing bore of the improved high performancealuminum connecting rod of the present invention remains within 0.0003to 0.0005 inch of its original dimension after one run at full load, ascompared to the bearing housing bore of a conventional high performancealuminum connecting rod, which loses roundness of 0.001 to 0.0015 inchafter one run at full load. These increases in strength and performanceare particularly significant in view of the fact that conventional highperformance aluminum connecting rod made of 7075-T6 were the state ofthe art prior to the development of the improved high performancealuminum connecting rod of the present invention.

It may therefore be seen that the present invention teaches an improvedhigh performance aluminum connecting rod made of an improved materialcapable of withstanding the high compressive loads of current dragracing engine technology. The material used by the improved highperformance aluminum connecting rod of the present invention haslightweight construction which is comparable to presently known highperformance aluminum materials such as 7075-T6, while possessingsubstantially enhanced compression yield strength characteristics ascompared to such presently known materials. In addition, this improvedmaterial also retains or enhances all of the other favorable materialcharacteristics of such presently known materials.

The improved high performance aluminum connecting rod of the presentinvention is readily susceptible of manufacture by conventional forgingtechniques, with the forged part being readily machinable to therequired finished dimensions. The high performance characteristics ofthe aluminum material used to make the improved high performancealuminum connecting rod of the present invention are not adverselyaffected in either the forging or machining operations. Mostimportantly, the improved high performance aluminum connecting rod ofthe present invention has sufficiently improved compression yieldstrength so as to hold both its dimensional length and the dimensionalroundness of the wrist pin bore and the bearing housing bore.

The improved high performance aluminum connecting rod of the presentinvention is of a construction which is both durable and long lasting,and which will remain within dimensional specifications throughout anextended operating lifetime. The improved high performance aluminumconnecting rod of the present invention is also of relativelyinexpensive construction to enhance its market appeal and to therebyafford it the broadest possible market. Finally, all of the aforesaidadvantages and objectives of the improved high performance aluminumconnecting rod of the present invention are achieved without incurringany substantial relative disadvantage.

DESCRIPTION OF THE DRAWINGS

These and other advantages of the improved high performance aluminumconnecting rod of the present invention are best understood withreference to the drawings, in which:

FIG. 1 is an isometric view of a rectangular bar stock blank which maybe forged and machined into the improved high performance aluminumconnecting rod of the present invention;

FIG. 2 is an isometric view of a round bar stock blank which may be usedinstead of the rectangular bar stock blank illustrated in FIG. 1;

FIG. 3 is an isometric view of a blocker die for use in rough forgingthe rectangular bar stock blank illustrated in FIG. 1 into a roughforging;

FIG. 4 is an isometric view of a finisher die for use in finishing therough forging produced by the blocker die illustrated in FIG. 3;

FIG. 5 is an isometric view of a trim die for use in trimming theflashing off of the finished forging produced by the finisher dieillustrated in FIG. 4;

FIG. 6 is a side plan view of the improved high performance aluminumconnecting rod of the present invention which has been machined from thetrimmed forging produced by the trim die illustrated in FIG. 5;

FIG. 7 is an edge plan view of the improved high performance aluminumconnecting rod illustrated in FIG. 6;

FIG. 8 is an enlarged view of a portion of the improved high performancealuminum connecting rod illustrated in FIGS. 6 and 7, showing themutually engaging serrated surfaces which have been machined into thecap and the fork of the connecting rod;

FIG. 9 is a cross-sectional edge view of the improved high performancealuminum connecting rod illustrated in FIGS. 6 and 7, showing keyways(bearing tang grooves) and a bearing retaining pin lock aperturemachined into the bearing housing bore, and an oil passage machined intothe wrist pin bore;

FIG. 10 is a bottom plan view of the cap illustrated in FIGS. 6, 7, and9; and

FIG. 11 is a partial sectional view from the side of the improved highperformance aluminum connecting rod illustrated in FIGS. 6, 7, and 9,including the cap illustrated in FIGS. 6, 7, 9, and 10, and showing tworod bolts which are used to retain the cap on the fork of the connectingrod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the improved high performance aluminumconnecting rod of the present invention will be described in detail, butfirst the high performance aluminum alloy from which it is manufacturedwill be described in detail. As mentioned above, this high performancealuminum alloy is a variant of the aluminum alloy taught in Alcoa's U.S.Pat. No. 5,221,377, which has previously been incorporated herein byreference. Prior to the development leading up to the improved highperformance aluminum connecting rod of the present invention, thisaluminum alloy has not been known to be suitable for the fabrication ofconnecting rods.

The preferred high performance aluminum alloy used to make the improvedhigh performance aluminum connecting rod of the present invention is analloy available from Alcoa as 7055-T77511, also referred to as HP007.This aluminum alloy has been available from Alcoa for some time, butnever made into extruded bar stock for forging. By working with Alcoa,the inventors of the invention described herein obtained 7055-T077511aluminum alloy from Alcoa in extruded bar stock suitable for forging.The 7055-T77511 aluminum alloy used to fabricate the improved highperformance aluminum connecting rod of the present invention isformulated (by weight) as follows:

Material Percentage by Weight

SI 0.10

FE 0.15

CU 2.0-2.6

MN 0.05

MG 1.8-2.3

CR 0.04

ZN 7.6-8.4

ZR 0.08-0.25

TI 0.06

AL balance

In accord with the present invention, the 7055-T77511 aluminum alloy isprovided as extruded bar stock which is suitable for forging, and may beeither rectangular bar stock or round bar stock. Typically, arectangular bar stock can be used to make a billet rod that is notforged. If rectangular bar stock is used as a blank for the forgingoperation, it is preferably between 1.0 and 2.5 inches in thickness,between 2.0 and 5.0 inches wide, and between 6.0 and 15.0 inches long.The preferred dimensions for a rectangular bar stock blank areapproximately 1.5 inches in thickness, approximately 4.0 inches wide,and approximately 12.5 inches long. Such a rectangular bar stock blank20 is illustrated in FIG. 1. Generally, the length should fill the die,but not be so long as to present the possibility of breaking the die.

If round bar stock is used as a blank for the forging operation, it ispreferably between 1.5 and 2.5 inches in diameter, and between 11.5 and14.5 inches long. The preferred dimensions for a round bar stock blankare approximately 2.0 inches in diameter, and approximately 12.5 incheslong. Such a round bar stock blank 22 is illustrated in FIG. 2.

The single most critical portion of the manufacture of the improved highperformance aluminum connecting rod of the present invention is theforging operation, which in large part determines the characteristics ofthe complete connecting rod. The temperature that the rectangular barstock blank 20 or the round bar stock blank 22 is heated to for theforging operation is critical. In the development of the improved highperformance aluminum connecting rod of the present invention, asubstantial amount of testing was required in order to establish thetemperature range which would produce a product with acceptable materialcharacteristics, since the 7055-T77511 high performance aluminum alloyhad never been supplied as extruded forging stock, far less been used tomanufacture connecting rods.

In the experimental work on prototype forgings, machining revealedcracks in the vicinity of the bearing housing bore. In fact,approximately 20-25 percent of the prototype connecting rods were foundto be cracked near the bearing housing bore. The experimental work whichwas performed included chemistry comparisons, mechanical propertycomparisons, and extrusion parameter comparisons of the 7055-T77511 highperformance aluminum alloy; met allographic examinations and ultrasonicexaminations of the bar stock; failure analyses of the connecting rods,which included ultrasonic examination of the connecting rods, macroetching of the connecting rods to examine material flow during forging,and met allographic examination of the connecting rods; and forgingtrials to duplicate failures and identify the causes therefore,including jogging samples, and forging temperature trials.

The results of this experimental work reduced the possible causes one byone. The chemical composition of three different lots was nearlyidentical. The mechanical properties of the three different lots weresubstantially similar. The actual extrusion parameters for the threedifferent lots were also substantially similar.

The met allographic examinations of the bar stock revealed no materialdiscontinuities. Similarly, the ultrasonic examination of the bar stockrevealed no material discontinuities.

Macro etching of the connecting rods found no differences in materialflow when comparing good connecting rods to failed connecting rods. Metallographic examination of failed connecting rods revealed internalvoids.

Jogging samples during forging trials did not duplicate the failuremode. Finally, the cause of the failure was determined to be caused by atotally unexpected cause, namely forge slug temperatures above 800°Fahrenheit. Whenever the forge slug was heated to temperatures ofapproximately 800° Fahrenheit or above, internal voids resulted. Thevoids were quite small at approximately 800° Fahrenheit, and becameprogressively larger at higher temperatures.

Thus, 800° Fahrenheit was identified as the slug temperature at the topof the range of temperatures which could produce acceptable forgings.The lowest slug temperature which could be used was identified as 500°Fahrenheit. The optimum slug temperature was identified to beapproximately 775° Fahrenheit.

Extruded bar stock is preferred but rectangular bar stock can be used. Ablocker die used to rough out the rectangular bar stock blank 20 isillustrated in FIG. 3. Blocker die halves 30 and 32 are shown with therectangular bar stock blank 20 located therebetween. The forgingoperation is illustrated in FIG. 3, with the rectangular bar stock blank20 heated to the forging temperature, which in the preferred embodimentis approximately 775° Fahrenheit. The heated rectangular bar stock blank20 is the forging slug. The blocker die half 30 is hit, forcing ittoward the blocker die half 32, forming the heated rectangular bar stockblank 20 into a rough forging 34 (which is illustrated in FIG. 4). Inthe preferred embodiment, the forging slug is struck only once in theblocker die.

A finisher die used to finish the rough forging 34 is illustrated inFIG. 4. Finisher die halves 36 and 38 are shown with the rough forging34 located therebetween. The finishing forging operation illustrated inFIG. 4 is performed immediately after the rough forging operationillustrated in FIG. 3. The finsher die half 36 is hit, forcing it towardthe finisher die half 38, forming the rough forging 34 into a finishedforging 40 (which is illustrated in FIG. 5). In the preferredembodiment, the rough forging 34 is truck in the finisher die, diecleaned, and hit again.

A trim die used to trim the flashing (indicated generally by thereference numeral 42) from the finished forging 40 is illustrated inFIG. 5. Trim die halves 44 and 46 are shown with the finished forging 40located therebetween. The trimming operation illustrated in FIG. 5 isperformed after cooling to room temperature after the finishing forgingoperation illustrated in FIG. 4. The trim die half 44 is hit, forcing ittoward the trim die half 46, trimming the flashing 42 from the finishedforging 40 and completing the forging operation. In the preferredembodiment, the finished forging 40 need be struck only once in the trimdie.

The connecting rod forging is then heat treated, following which it isetched. At this point, the connecting rod forging is then penetrantinspected and ultrasonically tested in order to detect any latentdefects. The connecting rod forging is then ball burnished, whichcompletes the portion of the manufacturing process prior to machining.

The various machining steps required to complete the manufacture of theimproved high performance aluminum connecting rod 50 will be describedwith reference to the remaining figures, which show the improved highperformance aluminum connecting rod 50 in its completed form. Referringfirst to FIGS. 6 and 7, the improved high performance aluminumconnecting rod 50 is illustrated with its pin end on the right and itscrank end at the left. A wrist pin bore 52 is illustrated in the pin endof the improved high performance aluminum connecting rod 50, and abearing housing bore 54 is illustrated in the crank end of the improvedhigh performance aluminum connecting rod 50.

The improved high performance aluminum connecting rod 50 is split toform a cap 56 and a fork 58 of the improved high performance aluminumconnecting rod 50. (As mentioned above, the cap 56 and the balance ofthe improved high performance aluminum connecting rod 50 mayalternatively be forged as two separate segments.) As best illustratedin FIG. 6, the split between the cap 56 and the fork 58 is defined by aplane which can be orthogonal or at any angle to the longitudinal axisof the improved high performance aluminum connecting rod 50 (the axisextending between the pin end and the crank end of the improved highperformance aluminum connecting rod 50), which plane divides the bearinghousing bore 54 at the crank end of the improved high performancealuminum connecting rod 50 in half. The portion of the improved highperformance aluminum connecting rod 50 located between the fork 58 andthe rod end of the improved high performance aluminum connecting rod 50forms the rod beam 60 of the improved high performance aluminumconnecting rod 50.

As mentioned above, there are three methods which may be used to removethe cap 56 from the fork 58 of the improved high performance aluminumconnecting rod 50, all of which are conventional in the art. Thesemethods include sawing the cap 56 from the fork 58 of the improved highperformance aluminum connecting rod 50, using a laser to divide the cap56 from the fork 58 of the improved high performance aluminum connectingrod 50, and fracturing the cap 56 from the fork 58 of the improved highperformance aluminum connecting rod 50. While the first two methods areself-explanatory, examples of fracturing the cap 56 from the fork 58 ofthe improved high performance aluminum connecting rod 50 are provided inU.S. Pat. No. 5,105,538, to Hoag et al., U.S. Pat. No. 5,507,093, toWittenstein et al., and U.S. Pat. No. 5,655,296, to Ravenhorst et al.U.S. Pat. No. 5,105,538, U.S. Pat. No. 5,507,093, and U.S. Pat. No.5,655,296 are each hereby incorporated herein by reference.

Following the separation of the cap 56 from the fork 58 of the improvedhigh performance aluminum connecting rod 50, a radius approximately0.005 larger than the finished radius of the bearing housing bore 54 ismachined into both the cap 56 and the fork 58. Referring particularly toFIG. 8 in addition to FIGS. 6, 7, and 9, in the preferred embodiment ofthe present invention, the adjoining faces of the cap 56 and the fork 58of the improved high performance aluminum connecting rod 50 are machinedinto mutually engaging serrated surfaces 62 and 64, respectively.

Referring now to FIGS. 6, 7, 9, and particularly 10 and 11, two holes 66and 68 are drilled into the cap 56. The holes 66 and 68 are located inthe cap 56 on opposite sides of the bearing housing bore 54, and areparallel to the axis of the improved high performance aluminumconnecting rod 50 (which extends between the rod end and the crank endof the improved high performance aluminum connecting rod 50). Referringparticularly to FIG. 11, two smaller holes 70 and 72 are drilled intothe fork 58 of the improved high performance aluminum connecting rod 50.The holes 70 and 72 are located in the fork 58 on opposite sides of thebearing housing bore 54, and are coaxial with the holes 66 and 68 in thecap 56. The holes 70 and 72 in the fork 58 of the improved highperformance aluminum connecting rod 50 are threaded.

Next, the cap 56 is assembled onto the fork 58 of the improved highperformance aluminum connecting rod 50 using two rod bolts 74 and 76,which are, by way of example, 7/16-20 UNFJ Class 3A bolts with aRockwell of 51 c to 52 c, rated at 272 ksi. The rod bolts 74 and 76 arepreferably lubricated with S.A.E. 30 weight motor oil, and are torquedto the proper degree, preferably approximately 85 Ft. Lbs.

Four keyways, (bearing tang grooves) two of which are referred to by thereference numerals 78 and 80, are machined into the cap 56 and the fork58 in the bearing housing bore 54 at the location of the split betweenthe cap 56 and the fork 58, as best illustrated in FIG. 9. The other twokeyways which are not illustrated herein are located on the oppositeside of the bearing housing bore 54 from the keyways 78 and 80. Alsomachined into the bearing housing bore 54 in the cap 56 is a bearing pinlock aperture 82, which is illustrated in FIG. 9. An oil passage 84,which is also illustrated in FIG. 9, is machined into the wrist pin bore52.

Following the assembly of the cap 56 to the fork 58 of the improved highperformance aluminum connecting rod 50 using the rod bolts 74 and 76,the bearing housing bore 54 is then rough bored, finish bored, and honedto the proper size. On the pin end of the improved high performancealuminum connecting rod 50, the wrist pin bore 52 is bored and honed tothe proper size. This completes the manufacture of the improved highperformance aluminum connecting rod 50 of the present invention.

It may therefore be appreciated from the above detailed description ofthe preferred embodiment of the present invention that it teaches animproved high performance aluminum connecting rod made of an improvedmaterial capable of withstanding the high compressive loads of currentdrag racing engine technology. The material used by the improved highperformance aluminum connecting rod of the present invention haslightweight construction which is comparable to presently known highperformance aluminum materials such as 7075-T6, while possessingsubstantially enhanced compression yield strength characteristics ascompared to such presently known materials. In addition, this improvedmaterial also retains or enhances all of the other favorable materialcharacteristics of such presently known materials.

The improved high performance aluminum connecting rod of the presentinvention is readily susceptible of manufacture by conventional forgingtechniques, with the forged part being readily machinable to therequired finished dimensions. The high performance characteristics ofthe aluminum material used to make the improved high performancealuminum connecting rod of the present invention are not adverselyaffected in either the forging or machining operations. Mostimportantly, the improved high performance aluminum connecting rod ofthe present invention has sufficiently improved compression yieldstrength so as to hold both its dimensional length and the dimensionalroundness of the wrist pin bore and the bearing housing bore.

The improved high performance aluminum connecting rod of the presentinvention is of a construction which is both durable and long lasting,and which will remain within dimensional specifications throughout anextended operating lifetime. The improved high performance aluminumconnecting rod of the present invention is also of relativelyinexpensive construction to enhance its market appeal and to therebyafford it the broadest possible market. Finally, all of the aforesaidadvantages and objectives of the improved high performance aluminumconnecting rod of the present invention are achieved without incurringany substantial relative disadvantage.

Although an exemplary embodiment of the improved high performancealuminum connecting rod of the present invention has been shown anddescribed with reference to particular embodiments and applicationsthereof, it will be apparent to those having ordinary skill in the artthat a number of changes, modifications, or alterations to the inventionas described herein may be made, none of which depart from the spirit orscope of the present invention. All such changes, modifications, andalterations should therefore be seen as being within the scope of thepresent invention.

What is claimed is:
 1. A high performance aluminum connecting rod providing a long service life without substantial elongation or deformation in a high performance engine, said connecting rod comprising: an extruded aluminum alloy bar stock blank, comprising 7055-T77511 aluminum alloy material which has been forged at a forging temperature ranging from approximately 500 degrees Fahrenheit to approximately 800 degrees Fahrenheit and machine finished.
 2. An aluminum connecting rod as defined in claim 1, wherein said connecting rod is extruded from an aluminum alloy bar stock blank between approximately 1.0 and 2.5 inches in thickness, between approximately 2.0 and 5.0 inches wide, and between approximately 6.0 to 15.0 inches long.
 3. An aluminum connecting rod as defined in claim 2, wherein said piece of rectangular bar stock is approximately 1.5 inches in thickness, approximately 4.0 inches wide, and approximately 12.5 inches long.
 4. An aluminum connecting rod as defined in claim 1, wherein said connecting rod was extruded from an aluminum alloy bar stock blank between approximately 1.5 and 2.5 inches in diameter, and between approximately 11.5 and 14.5 inches long.
 5. An aluminum connecting rod as defined in claim 1, wherein said connecting rod comprises: a wrist pin bore located at a pin end thereof; and a bearing housing bore located at a crank end thereof, a longitudinal axis being defined between said pin end of said connecting rod forging and said crank end of said connecting rod forging; and wherein said crank end of said connecting rod forging is split into a cap located at the distal end of said crank end and a fork by a plane which is essentially orthogonal to said longitudinal axis and which divides said bearing housing bore in half.
 6. An aluminum connecting rod as defined in claim 5, wherein said connecting rod comprises: a pair of holes in said cap on opposite sides of said bearing housing bore and which holes are parallel to said longitudinal axis; and two threaded holes in said fork, on opposite sides of said bearing housing bore and being coaxial with said holes in said cap and said cap being attached by two rod bolts which are inserted through said two holes in said cap and screwed into said two threaded holes in said fork.
 7. An aluminum connecting rod as defined in claim 6, wherein said high performance aluminum connecting rod has a compressive yield strength of approximately 90 ksi.
 8. A high performance aluminum connecting rod, providing a long service life without substantial elongation or deformation in a high performance engine, said connecting rod comprising: an extruded aluminum alloy bar stock blank, said aluminum alloy consisting essentially of, by weight, about 7.6 to 8.4 percent zinc, about 1.8 to 2.3 percent magnesium, about 2.0 to 2.6 percent copper, and about 0.08 to 0.25 percent zirconium, the balance comprising substantially aluminum and containing other incidental elements and impurities which has been forged at a forging temperature having a range from approximately 500 degrees Fahrenheit to approximately 800 degrees Fahrenheit and machine finished.
 9. An aluminum connecting rod as defined in claim 8, wherein said aluminum alloy comprises, by weight, about 0.05 percent manganese.
 10. An aluminum connecting rod as defined in claim 8, wherein said aluminum alloy comprises, by weight, no more than about 0.4 percent total iron, silicon, and other impurities.
 11. The aluminum connecting rod as defined in claim 8, wherein said aluminum alloy comprises, by weight, about 0.10 percent manganese and about 0.15 percent iron.
 12. The aluminum connecting rod as defined in claim 8, wherein said aluminum alloy comprises one or more of, by weight, about 0.10 percent silicon, about 0.15 percent iron, about 0.05 percent manganese, about 0.04 percent chromium, and about 0.06 percent titanium.
 13. The aluminum connecting rod as defined in claim 8, wherein said high performance aluminum connecting rod has a compressive yield strength of approximately 90 ksi.
 14. A high performance light weight aluminum connecting rod providing a long service life without substantial deformation or elongation in a high performance engine without compromising strength characteristics, said connecting rod comprising: an extruded aluminum alloy bar stock blank, said aluminum alloy consisting essentially of, by weight, about 7.6 to 8.4 percent zinc, about 1.8 to 2.3 percent magnesium, about 2.0 to 2.6 percent copper, about 0.08 to 0.25 percent zirconium, about 0.10 percent silicon, about 0.15 percent iron, about 0.05 percent manganese, about 0.04 percent chromium, and about 0.06 percent titanium, the balance comprising substantially aluminum and impurities and which has been forged at a forging temperature having a range from approximately 500 degrees Fahrenheit to approximately 800 degrees Fahrenheit.
 15. The aluminum connecting rod as defined in claim 14, wherein said forged connecting rod is machined into a finished connecting rod having improved compressive yield strength with a relatively long operating life without compromising dimensional parameters.
 16. The aluminum connecting rod as defined in claim 15, wherein extruded aluminum alloy bar stock is heated to a forging temperature of approximately 775 degrees Fahrenheit to obtain said connecting rod.
 17. The aluminum connecting rod as defined in claim 15, wherein said high performance aluminum connecting rod has a compressive yield strength of approximately 90 ksi.
 18. An aluminum connecting rod as defined in claim 15, wherein said connecting rod comprises: a wrist pin bore located at a pin end thereof; and a bearing housing bore located at a crank end thereof, a longitudinal axis being defined between said pin end of said connecting rod forging and said crank end of said connecting rod forging; and wherein said crank end of said connecting rod forging is split into a cap located at the distal end of said crank end and a fork by a plane which is essentially orthogonal to said longitudinal axis and which divides said bearing housing bore in half; a pair of holes in said cap on opposite sides of said bearing housing bore and which holes are parallel to said longitudinal axis; and two threaded holes in said fork, on opposite sides of said bearing housing bore and being coaxial with said holes in said cap and said cap being attached by two rod bolts which are inserted through said two holes in said cap and screwed into said two threaded holes in said fork.
 19. A light weight high performance aluminum connecting rod which does not suffer substantial elongation or deformation under high performance conditions without compromising strength characteristics and which is made by the method comprising: providing an extruded aluminum alloy bar stock blank, said aluminum alloy comprising 7055-T77511 aluminum alloy material capable of withstanding high compressive loading; heating said extruded aluminum alloy bar stock blank to a forging temperature having a range from approximately 500° Fahrenheit to approximately 800° Fahrenheit; forging said heated extruded aluminum alloy bar stock blank into a connecting rod forging; and machining said connecting rod forging into a finished connected rod having improved compressive yield strength with a relatively long operating life without compromising dimensional parameters.
 20. A connecting rod as defined in claim 19, wherein said method of making the connecting rod in the heating step comprises: heating said extruded aluminum alloy bar stock blank to a forging temperature between approximately 750 degrees Fahrenheit and approximately 800 degrees Fahrenheit.
 21. A connecting rod as defined in claim 19, wherein said method of making the connecting rod in the heating step comprises: heating said extruded aluminum alloy bar stock blank to a forging temperature of approximately 775 degrees Fahrenheit.
 22. A connecting rod as defined in claim 19, wherein said method of making the connecting rod in the forging step comprises: first, forging said heated extruded aluminum alloy bar stock blank into a rough forging in a blocker die; and second, forging said rough forging into a finished forging in a finisher die.
 23. A connecting rod as defined in claim 19, wherein said method of making the connecting rod comprises using a forging having: a wrist pin bore located at a pin end thereof; and a bearing housing bore located at a crank end thereof, a longitudinal axis being defined between said pin end of said connecting rod forging and said crank end of said connecting rod forging; and wherein said crank end of said connecting rod forging is split into a cap located at the distal end of said crank end and a fork by a plane which is essentially orthogonal to said longitudinal axis and which divides said bearing housing bore in half.
 24. A connecting rod as defined in claim 23, wherein said method of making the connecting rod in the machining step comprises: machining said wrist pin bore to a specified diameter; and machining said bearing housing bore to a specified diameter.
 25. A connecting rod as defined in claim 23, wherein said method of making the connecting rod in the machining step comprises: machining adjoining faces of said cap and said fork into mutually engaging serrated surfaces.
 26. A connecting rod as defined in claim 23, wherein said method of making the connecting rod comprises: drilling two holes into said cap on opposite sides of said bearing housing bore, which holes are parallel to said longitudinal axis; and drilling and tapping two threaded holes into said fork, said threaded holes being located in said fork on opposite sides of said bearing housing bore and being coaxial with said holes in said cap.
 27. A connecting rod as defined in claim 26, where the method of making the rod additionally comprises: attaching said cap to said fork by two rod bolts which are inserted through said two holes in said cap and are screwed into said two threaded holes in said fork.
 28. A connecting rod as defined in claim 23, wherein said high performance aluminum connecting rod has a compressive yield strength of approximately 90 ksi.
 29. A high performance light weight aluminum connection rod which does not suffer substantial elongation or deformation under high performance conditions without compromising strength characteristics, which is made by the method comprising: providing an extruded aluminum alloy bar stock blank, said aluminum alloy consisting essentially of, by weight, about 7.6 to 8.4 percent zinc, about 1.8 to 2.3 parent magnesium, about 2.0 to 2.6 percent copper, and about 0.08 to 0.25 percent zirconium, the balance comprising substantially aluminum and containing other incidental elements and impurities and which aluminum alloy is capable of withstanding high compressive loading; heating said extruded aluminum alloy bar stock blank to a forging temperature having a range from approximately 500° Fahrenheit to approximately 800 degrees Fahrenheit; forging said heated extruded aluminum alloy bar stock blank into a connecting rod forging; and machining said connecting rod forging into a finished connecting rod having improved compressive yield strength with a relatively long operating life without compromising dimensional parameters.
 30. A connecting rod as defined in claim 29, wherein said aluminum alloy comprises one or more of, by weight, about 0.10 percent silicon, about 0.15 percent iron, about 0.05 percent manganese, about 0.04 percent chromium, and about 0.06 percent titanium.
 31. A connecting rod as defined in claim 29, wherein said method of making the connecting rod in the heating step comprises: heating said extruded aluminum alloy bar stock blank to a forging temperature of approximately 775 degrees Fahrenheit.
 32. A connecting rod as defined in claim 29, wherein said high performance aluminum connecting rod has a compressive yield strength of approximately 90 ksi.
 33. A high performance aluminum connecting rod providing a long service life without substantial elongation or deformation in a high performance engine, said connecting rod comprised essentially of an extruded 7055-T77511 aluminum alloy material and which is also comprised of a wrist pin bore located at a pin end thereof; and a bearing housing bore located at a crank end thereof.
 34. An aluminum connecting rod as defined in claim 33, wherein said connecting has a longitudinal axis being defined between said pin end of said connecting rod forging and said crank end of said connecting rod forging; and wherein said crank end of said connecting rod forging is split into a cap located at the distal end of said crank end and a fork by a plane which is essentially orthogonal to said longitudinal axis and which divides said bearing housing bore in half.
 35. An aluminum connecting rod as defined in claim 34, wherein said connecting rod comprises: a pair of holes in said cap on opposite sides of said bearing housing bore and which holes are parallel to said longitudinal axis; and two threaded holes in said fork, on opposite sides of said bearing housing bore and being coaxial with said holes in said cap and said cap being attached by two rod bolts which are inserted through said two holes in said cap and screwed into said two threaded holes in said fork.
 36. An aluminum connecting rod as defined in claim 33, wherein connecting rod is extruded from an aluminum alloy bar stock blank between approximately 1.0 and 2.5 inches in thickness, between approximately 2.0 and 5.0 inches wide, and between approximately 6.0 to 15.0 inches long.
 37. A high performance aluminum connecting rod, providing a long service life without substantial elongation or deformation in a high performance engine, said connecting rod being comprised of an extruded aluminum alloy consisting essentially of, by weight, about 7.6 to 8.4 percent zinc, about 1.8 to 2.3 percent magnesium, about 2.0 to 2.6 percent copper, and about 0.08 to 0.25 percent zirconium, the balance comprising substantially aluminum and containing other incidental elements and impurities, said connecting rod further comprising a wrist pin bore located at a pin end thereof and a bearing housing bore located at a crank end thereof.
 38. An aluminum connecting rod as defined in claim 37, wherein said aluminum alloy comprises, by weight, about 0.05 percent manganese.
 39. An aluminum connecting rod as defined in claim 37, wherein said aluminum alloy comprises, by weight, no more than about 0.4 percent total iron, silicon, and other impurities.
 40. The aluminum connecting rod as defined in claim 37, wherein said aluminum alloy comprises, by weight, about 0.10 percent manganese and about 0.15 percent iron.
 41. The aluminum connecting rod as defined in claim 37, wherein said aluminum alloy comprises one or more of, by weight, about 0.10 percent silicon, about 0.15 percent iron, about 0.05 percent manganese, about 0.04 percent chromium, and about 0.06 percent titanium.
 42. A high performance light weight aluminum connecting rod providing a long service life without substantial deformation or elongation in a high performance engine without compromising strength characteristics, said connecting rod comprising an extruded aluminum alloy consisting essentially of, by weight, about 7.6 to 8.4 percent zinc, about 1.8 to 2.3 percent magnesium, about 2.0 to 2.6 percent silicon, about 0.15 percent iron, about 0.05 percent manganese, about 0.04 percent chromium, and about 0.06 percent titanium, the balance comprising substantially aluminum and impurities.
 43. An aluminum connecting rod as defined in claim 42, wherein said connecting rod comprises: a wrist pin bore located at a pin end thereof; and a bearing housing bore located at a crank end thereof, a longitudinal axis being defined between said pin end of said connecting rod forging and said crank end of said connecting rod forging; and wherein said crank end of said connecting rod forging is split into a cap located at the distal end of said crank end and a fork by a plane which is essentially orthogonal to said longitudinal axis and which divides said bearing housing bore in half; a pair of holes in said cap on opposite sides of said bearing housing bore and which holes are parallel to said longitudinal axis; and two threaded holes in said fork, on opposite sides of said bearing housing bore and being coaxial with said holes in said cap and said cap being attached by two rod bolts which are inserted through said two holes in said cap and screwed into said two threaded holes in said fork. 